What are the components of automation?

Machine Automation Basics

• By Chip McDaniel
• InTech

Summary

Fast Forward

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• Power needs to be distributed to a machine’s motors, drives, controllers, and other components.
• The machine’s safety system must remove motion-causing energy when called upon, including both electrical and fluid power.
• It is a good practice to have multiple Ethernet and serial ports available to integrate to a variety of equipment, computers, HMIs, and business and enterprise systems.

Systems Integration

By Chip McDaniel

Faced with ever-increasing cost pressures and demands for improved performance, machine builders are actively seeking new automation solutions with improved cost/performance ratios. In response, vendors must often incorporate commercial off-the-shelf components and other technologies to deliver more performance at lower costs in smaller form factors.

This article shows how machine builders and vendors can work together to deliver the automation systems demanded and how to successfully integrate the multiple power and control subsystems and components.

Components of Automation

A machine's automation system primarily consists of power and control components. For smaller machines, these may be housed in one panel; whereas larger machines may require multiple panels, often one for control and another for power. The main subsystems and components of a machine automation system are:

• Power distribution
• Motor control and drives
• Safety system
• Programmable controllers
• Discrete and analog I/O
• Communication systems
• Human-machine interface (HMI)

The power distribution subsystem feeds power to components such as motors, drives, and controllers. The control subsystem primarily consists of safety systems, programmable controllers, discrete and analog I/O, communication systems, and HMIs. Let's dive into each of these areas in more detail.

Power Distribution

The National Electric Code (NEC, also NFPA 70) has extensive guidelines to ensure safe electricity usage, protecting both persons and property. Before the power source connects to the machine control enclosure via a plug, disconnect, or terminal block, the NFPA 79: Electrical Standard for Industrial Machinery governs industrial machine safety to mitigate fire and electrical hazards. Key requirements include using proper disconnect means, protecting personnel from electrical hazards, and protecting equipment from overcurrent and overloads.

The disconnect, whether a switch, circuit breaker, or plug cord, must be installed for any enclosure fed with voltages of 50 VAC or more. It should be appropriately sized, positioned, wired, labeled, and in some cases, interlocked with the enclosure door.

Personnel protection from electrical hazards is crucial both inside and outside a machine's power or control panel. All conductors must be safeguarded from contact. Power distribution devices typically include this level of protection, but live components such as power buses and distribution blocks should be covered with a non-conductive, transparent cover.

Protecting equipment from overcurrent is vital to reduce fire risks. Conductors and electrical components must be shielded from short-circuits. Overcurrent protection devices like fuses and circuit breakers must be appropriately sized based on conductor current capacity, device interrupt rating, maximum fault current, system voltage, load characteristics, and other factors.

For power circuits, branch-circuit-rated devices are required to meet current-limiting and ground fault protection standards. Supplemental overcurrent devices work well in downstream control circuits tapped from the branch circuit's load side but are unsuitable for use in power circuits.

Motor Control and Drives

Motors have specific needs in machine control, requiring proper electrical control, from simple on/off setups to sophisticated variable speed applications. Motor control devices include manual motor starters, motor contactors, starters with overloads, drives, and soft starters.

A motor circuit must include both overcurrent and overload protection, typically achieved using branch-circuit protection like fuses and motor starters with overload devices. Additional protection for components considers factors such as loss of cooling, abnormal temperatures, ground fault protection, over/under voltage, lightning, overspeed, and loss of voltage in three-phase supplies.

Some motor controllers, like drives and combination controllers, are self-protected. If so, the manufacturer's instructions will specify that the device is suitable for protecting output conductors.

Safety System

A risk assessment drives the design of the safety system, which removes motion-causing energy, including electrical and fluid power, to safely stop the equipment and protect personnel and machines. Numerous safety standards apply to machine control at both mechanical and electrical levels. Proper mechanical guarding, access points, and hazard elimination are crucial.

In small machine control applications, a safety relay often integrates safety functions for emergency stops, guard door monitoring, or operator protection via light curtains. Advanced machines use safety-rated controllers that simplify integrating multiple safety devices by reducing wired safety logic and allowing programmable safety functions.

Programmable Controllers and I/O

Programmable controllers, available in various sizes, include PLCs, PACs, or PCs. The machine control application's complexity, end-user specifications, and personal preference influence controller selection. Many vendors offer controller families that range from simple to complex applications, allowing for some standardization.

Using the same software platform to program a family of controllers is standard, letting designers initially program the system before selecting the appropriate controller based on I/O points, control capacity, and special functions. Capabilities like extensive communications and high-speed control should be carefully evaluated, as they often drive controller selection.

Discrete and analog I/O connect the controller to machine sensors and actuators. These signals can originate in the main control panel through a terminal strip to field devices, but a distributed I/O architecture is often better, positioning I/O points nearer to field devices and multiplexing multiple signals over a single cable.

IO-Link, a point-to-point serial protocol for small-scale distributed I/O, connects IO-Link-enabled devices to a master module, communicating data directly to a machine controller and delivering diagnostics and device status for enriched discrete or analog data.

Communication Systems

Modern machine control heavily relies on extensive communication capabilities. Multiple Ethernet and serial ports integrate various equipment, computers, HMIs, and business systems efficiently (figure 3).

High-speed Ethernet ports ensure responsive HMI communication, peer-to-peer networking, and business system connectivity. Industrial Ethernet protocols like EtherNet/IP and Modbus TCP/IP support scanner/client and adapter/server connections, enabling email, web server, and remote access functions—all crucial for machine control.

Legacy communication methods, such as serial RS-232 and RS-485, remain beneficial. Modern controllers often include USB and MicroSD communication and storage options.

Cybersecurity is also essential, with a layered defense approach recommended. Remote functions should be hardware-configured, and tags should be protected from remote access unless individually enabled.

Human-Machine Interface (HMI)

HMIs display critical machine data through graphical and textual views. They come as touch panels, text panels, message displays, or industrial monitors used for monitoring, control, status reporting, and more.

The HMI's purpose must be clear; some machines may need minimal control functions, while others require detailed status views, system parameter access, and recipe functionality. Defining the machine's requirements early helps determine HMI size and capabilities.

HMIs can also act as data hubs by connecting to multiple networked devices and are sometimes used for protocol conversion, enabling data exchange among various controllers and smart devices. Advanced HMIs support cloud data transfer and remote Internet access, secured by proper user authentication.

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